Cationic rosin sizes



CATIONIC ROSIN SIZES John H. Daniel, Jr., and Sewell T. Moore, Stamford, Conn., asslgnors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Applicafion July 28, 1954, Serial No. 446,396

Claims. (Cl. 92-3) The present invention relates to a novel cationic rosin size and to paper and other cellulosic webs sized therewith. The invention includes methods for manufacturing the size and applying the size in the manufacture of paper, etc.

In the past it has been customary to manufacture rosin sized paper by forming an aqueous dispersion of cellulosic papemnaking fibers, adding thereto an aqueous dispersion of rosin size formed by saponifying rosin with sodium or potassium hydroxide or carbonate, and precipitating the rosin on the fibers by the addition of alum. The fibers are then sheeted to form paper.

The manufacture of rosin sized paper according to the foregoing method has three principal disadvantages. In the first place, the rosin size described is anionic, and the alum is effective as a precipitant only when the pH of the fibrous suspension is acid. This acidity has a detrimental corrosive action on papermaking equipment and precludes the addition of an acid-sensitive filler such as calcium carbonate. Secondly, the paper itself has an acid pH, and acidity is known to have a weakening efiect upon cellulosic fibers. Thirdly, when the paper is made alkaline the rosin on the fibers is resaponified or otherwise rendered ineffective. This precludes the use of the paper for the wrapping of alkaline materials such as cement, plaster, or soap.

The discovery has now been made that the reaction products formed by heating a major amount of an ester gum (a rosin-polyhydric alcohol ester) with a minor amountof a water-soluble polyalkylenepolyamine, when solubilized by addition of a small amount of acid and dispersed in water, are colloidal, cationic sizing agents which are distinctively different from the heretofore known rosin .sizes of the soap or anionic type. The sizes of the present invention are substantive to cellulose fibers on contact therewith in aqueous suspension and therefore do not require the addition ofalum or other material as a precipitant. They are adsorbed by the fibers not only at acid pH values but also at alkaline pH values up to about 9. As a result, alkaline filling materials such as calcium carbonate may be added without harm, and the paper thus manufactured may be used in contact with alkaline materials.

The sizing agents of the present invention, when applied by the beater addition process, are added to a dilute aqueous suspension of cellulosic fibers in amount between about 1% and 5% based on the dry weight of the fibers. The agents are strongly cationic and are rapidly and substantively adsorbed by the fibers at any pH, not merely on the acid side down to about pH 4, but also on the alkaline side up to about pH 9. The thus sized fibers are formed into paper in the usual manner and the paper is heated between about 100 C. and 150 C. for /2 to 4 minutes to dry the paper and develop the water-resistant properties of the size. The sizes of the present invention do not undergo. chemical reaction or polymerization toany significant extent during this brief heating and it is therefore believed that the primary effect of the ited State patento 2,772,966 Patented Dec. 4, 1956 heating is to.soften or melt the particles of adsorbed size and permit them to flow along the fibers, thus greatly extending the fiber area protected. The sizing effect is principally due to the rosin component of the mixture and not to any of the solubilizing acid which may be present. p

The present invention makes possible the incorporation in the paper of the principal commercially used alkaline fillers including calcium carbonate, calcium silicate, Raffold (calcium carbonate-magnesium hydroxide), and calcium sulfite. These fillers are usually added in quantities ranging from about 5% to 100% of the dry weight of the paper fibers in order to obtain paper containing from about 2% to 30% of its weight of filler.

Moreover, the present invention permits the "addition of other conventional materials such as wax sizing emul- ICC such as corn starch, potato starch, and wheat starch;

locust bean gum and other mannogalactans; casein and other proteins; and similar gums, if necessary, solubilized with borax or other alkali. All these materials are preferably added after the sizing step has been completed.

The sizes may also be applied by the tub or impregnation method. in which a preformed cellulosic web is saturated by a direct impregnation or spraying with a dispersion of the size, the amount of the size being predetermined so that the web when dried contains from about 1% to 5% by weight of the material.

The sizes themselves are formed by a method which has as its principal step the reaction of an ester gum' at a suitable temperature of about 175 250 C. with a water-soluble polyalkylenepolyamine containing at least three nitrogen atoms. The reaction is continued at least to the point where a sample of the mixture (hereinafter termed the free base), when converted into a salt suchas the acetic acid salt, becomes dispersible in water. To perform this test, a sample of the molten free base is withdrawn, cooled to just above its flow point, and into it is stirred 1-2 mols of glacial acetic acid per mol 'of polyalkylenepolyamine present. to roonrtemperature, powdered, and one part of the powder is slowly added to 20 parts by weight of rapidly rosin nucleus. V A

agitated water at about the boil. Formation of a creamy, homogeneousemul-sion or dispersion demonstrates that sufficient reaction has taken place. Failure of the mixture to disperse in this manner is evidence that the reaction should be continued somewhat longer.

The sizing results obtained increase when the reaction is continued beyond the point at which the free base is barely dispersible when tested as described, and usually the reaction is best continued until the rate of decrease in alkalinity (as determined by titration of the samples of the reaction mixture with aqueous acid) falls to a low value as compared to the initial high value or becomes substantially constant.

Continuation of the reaction often has the beneficial effect of decreasing the emulsification temperature to the point where water having a temperature as low as C. or lower can be employed, with consequent savings in heat.

From consideration of the above-described decrease in alkalinity and increase in the water-dispersibility of the reaction mixture (as the acetate salt) it is believed that an exchange reaction takes place in which rosin residues are transferred from the polyhydric alcohol component of the ester gum to the polyalkylenepolyamine, the ester linkages being transformed during this. interchange into amide linkages. rosin group in an ester gum to one nitrogen atom in a polyalkylenepolyamine is illustrated by the following theoretical skeleton equation wherein R designates the The sample is cooled The interchange of one- H l l l l n-o-o-ort o 3 no-c in H1] I RC-1TI i I l Ester gum Polyalkylene- Size Polyhydric polyaminc (free base) alcohol The reaction usually does not. and need not go to completion, the extent of the reaction being sufiicient when a sample of the free base, when formed into a salt with acetic acid, etc. is dispersible in hot water. The free base and its salts are thus usually complex mixtures which are conveniently defined by their method of preparation.

The second part of the method consists in converting the modified rosin into a liquid size. This may be performed in several different ways, all essentially equivalent, each involving conversion of the rosin free base intov a salt. by addition of an acid or an acid-forming material, and dispersing the salt in water.

According to one method, particularly useful for commercial practice, an acid or acid-forming material such as epichlorohydrin is added to the molten free base. The product is cooled on a water-cooled drum provided with a scraping knife, flakes being obtained, and the flakes pulverized in a hammer. mill. The resulting powder is stable and can be shipped inbags. The powder is formed into a liquid size by the paper manufacturer by slowly flowing it into a volume of hot water with effective agitation. A creamy dispersion rapidly forms. Alternatively, the moltenreaction mixture after addition of the salt 'or salt-forming material may be flowed directly into hot agitated water. An emulsion likewise forms.

According to another method, the rosinated polyalkylenepolyamine in molten form is slowly poured into a volume of rapidly agitated boiling water containing 1-2 mols :of acid per mol of combined polyalkylenepolyamine present. A similar emulsion forms.

The emulsions formed by the. foregoing methods may be filtered to remove any insolubles present, and cooled. They appear to be indefinitely storage stable.

In the foregoing any of the commercially used rosins may be employed, including wood rosin, gum rosin, and tall oil rosin. These rosins are employed in the form of ester gum, that is, in the form of their esters with polyhydric alcohols such as glycol, glycerol, pentaerithritol, etc. The ester gums employed are widely known articles of commerce and may contain unreacted alcoholic hydroxyl groups. Such gums as glycol monorosinate and glycerolmonorosinate thereforefa-ll within the scope of the present invention.

The p'olyalkylenepolyamines employed in the present invention are a well-known class of compounds, preferred members known being the commercially available and readily prepared dieth'ylenetriamine, triethylenetetramine, tetraethylenepentamine, corresponding polypropylenepolyamines and polybutylenepolyamines, and analogues thereof. These compounds have the generic formula H2N(C1nH2mNY) CmH2mNHz wherein. Y represents H or CmH2mNI-Iz', m is an integer between 2 and 4 inclusive, and p is an integer between 1 and 4. Their chain length is not important in terms of results as the high molecular weight polyalkylenepolyamines formed by homopolymerizing low molecular alkyleneimines such as ethyleneirnine may .also be used, as well' as the high molecular amines formed by reacting simple polyalkylenepolyamines such as diethylenetria'rn'ine or 3,3-imin'obispropylamine with about 1 mol respectively of 1,3-dichloropropane or 1,2-dichloroethane. All these and similar polyalkylenepolyaminesare water-soluble and basic and are suitable for the practice of the present invention.

As amine-solubilizing acids there may be employed hydrochloric, formic, propionic, lactic, chloroacetic, and gly'c'olic acids. In place of these may be employed coinpounds which release acid radicals in situ such as epichlorohydrin, epibromohydrin, or dimethyl sulfate. Acetic acid is preferred, this material forming a salt of sufficiently low melting point as to permit the material to be dispersed in water without need for autoclave equipment while yielding a material which exhibits very satisfactory effectiveness as a size. Before addition of these agents the reaction mixtures are where necessary cooled to a temperature just above the point at which they are molten so as to minimize any side reactions which would otherwise take place as exemplified by the dehydration of acetic acid to form an amide. Such side reactions usually cause the efiicien'c'y 0f the product as a size to fall off.

In the principal reaction, the weight of reagents taken is determined by the ratio of the number of mols of combined rosin in. the ester gum to the number of nitrogen atoms of the polyalkylenep'olyamine. In general, the ratio of rosin radicals to nitrogen atoms should be between about 3:7 and 223, a smaller proportion of rosin radicals causing the water-resistance of the finished size cellulosic web to fall off rapidly, while a materially larger proportion results ina product which is quite difiicult to disperse even in boiling water at atmospheric pressure. Thus, when rosin triglyceride ester gum containing three rosin residues per molecule is reacted with diethylenetriamine containing three nitrogen atoms per molecule between about i and /3 mol of the ester gum should be taken per mol of the polyalkylenepolyamine; The ratio of 3:5 is preferred. With one mol of triethylenetetramine we therefore prefer to react 2.4 mols of combined rosin equivalent to 0.8 mol of rosin triglyceride. From. these examples, suitable proportions can readily be worked out for use in conjunction with other ester gums and polyalkylenepolyamines.

The amount of acetic or other acid which is thereafter added should be at least suflicient to permit ready dispersibility of the product. As little as 0.25 mol of acid per mol of combined polyalkylenepolyamine has been found sufiieient for this purpose, but somewhat more (preferably between about 1 and 2 mols) is more advantageous, these larger amounts doing no harm while avoiding the danger of adding too little.

The aqueous dispersions are formed at any convenient solids content from the point of view of viscosity. Before use in the manufacture of paper the dispersions are diluted to about l%-3% solids content with water to facilitate uniform distribution of the size among the fibers.

From the foregoing, it will be seen that broadly the sizing agents are produced by reacting an ester gum at about l75250 C. with a water-soluble polyalkylenepolyamine containing at least three nitrogen atoms (the ratio of the rosin radicals in the ester gum tothe nitrogen atoms of the polyalkylenepolyamine being between about 3:7 and 2:3) at least until the reaction product (or its acetate salt) forms a colloidal cationic dispersion when agitated with boiling water, and-adding from about A .toabout 2 mols of an amine. solubilizing acid per mol of polyalkylenepolyamine taken.

The paper and other cellulosic units ofthe present invention are sized by a uniformly distributed content. of the cationic rosin formed. by reacting an ester gum. with a water-soluble polyalkylenepolyamine in the-proportions and at least .to the extent setforth above.

The following examples constitute specific. embodiments of the invention, but are not to be construed as limitations thereon.

Example 1 The preparation ofa colloidal cationic rosin size according to the present inventionis illustrated by the following.

An ester gum was formed by heating 199 g. of N grade,

' heat-treated gum rosin (0.66 mol) and 0.03 gfof zinc oxide as catalyst in a reaction flask equipped with stirrer, thermometer, nitrogen gas inlet tube, and funnel to 260 'C., adding 24.5 g. of glycerol (0.266 mol) at that temperature over a period of three hours, and maintaining the temperature between about 270 C. and 275 C. for about eight additional hours at which point the product had an acid number of 8.4. During the reaction nitrogen :gas was passed through the mixture to sweep out water :as formed and minimize discoloration.

The ester gum thus formed was cooled to 180 C. and 38 g. of triethylenetetramine (0.26 mol) added over a period of ten minutes. (The ratio of rosin groups in the ester gum to the nitrogen atoms in the polyalkylenepoly- :aimine was 0.63.) The mixture was then maintained at 200 C. The course of the reaction was followed byv Example 2 The preparation of sized paper according to the present invention is illustrated by the following.-

A 60% bleached white-40% bleached soda pulp was beaten to a Green freeness of 340 ml. at a consistency of 2.5%. Three aliquots were withdrawn and diluted to 0.6% consistency with water. One was reserved as control. T o the remaining two was added 3.5% of the sizing solution of Example 1 (size solids on the dry weight of the fibers), previously diluted .to 1.5% solids by addition of water. The pH of the aliquots was then adjusted to the values shown in the table by the addition of aqueous NaOH or HCl as necessary. The samples were then stirred gently for five minutes and sheeted at light and heavy 'basis weights. The sheets were dried at 240 F. and conditioned for 24 hours at 73 F. and 50% relative humidity. The light sheets were tested for their dry tensile strength, dry bur-sting strength (Mullen) and water and ink resistance by the Currier and BKY methods respectively. The heavy sheets were tested by the Cobb method (15 minute contact time at 73 F.) to determine 5 Grams water absorbed per 100 cm.

From previous experience with similar sizes prepared by direct reaction of stearic acid with triethylenetetramine, it would have been expected that the application of this quantity of size to the fibers would have decreased the dry tensile and dry burst values of the resulting paper by about 75%. The results show that application of the sizes of the present invention caused only a 22% and 26% decrease in dry tensile strength and only a 29% and 32% decrease in burst. These values are quite acceptable commercially.

The Currier, BKY and Cobb values showed that the papers possessed very satisfactory resistance to water and ink.

. Example 3 p The procedure of Example 2 was repeated for the preparation of their sheets, except that 3% of papermak ers alum (based on the dry weight of the fibers) was added after addition of the size and before adjustment of the pH. Results are as follows:

Per- Sheet Dry Currier BKY Percent Size 1 cent pH 1 Basis Tens. (Slack) Ink, um Weight 1 Secs. Secs.

1 See table of Example 1.

These results in comparison with those of Example 1 show that the addition of alum effected a distinct increase in the Currier and ink-resistance values without significantly affecting the dry tensile values.

We claim:

1. A method of producing a rosinated polyalkylenepolyamine suitable for conversion to a cationic rosin sizing wherein Y represents a substituent selected from the group consisting of H and CmH2mNH2, m is an integer between 2 and 4 inclusive, and p is an integer between 1 and 4.

4. A method according to claim 1 wherein the ratio or rosin radicals to nitrogen atoms is about 3:5.

5. A sizing agent produced by the process of claim 1.

6. A method of producing a liquid cationic rosin size which comprises reacting an ester gum at about 250 C. with a Water-soluble polyalkylenepolyamine containing at least three nitrogen atoms, the ratio of the rosin radicals in said ester gum to the nitrogen atoms of said polyalkylenepolyamine being between about 3:7 and 2:3 at least until the reaction product as its acetate salt forms a colloidal dispersion when agitated with boiling water, adding from A to 2 mols of an amine-solubilizing acid per mol of combined polyalkylenepolyamine present, and dispersing the salt thus formed in water.

7. A size produced by the process of claim 6.

8. A method of producing a liquid cationic rosin size which comprises reacting an ester gum at about 175-250 C. with a water-soluble polyalkylenepolyamine containing at least three nitrogen atoms, the ratio of the rosin radicals in said ester gum to the nitrogen atoms of said polyalkylenepolyamine being between about 3:7 and 2:3, at least until the reaction product as its acetate salt forms a colloidal dispersion when agitated with boiling water, and dispersing the reaction product in water containing from about 1 to 2 mols of an amine-.solubilizing acid per mol of combined polyalkylenepolyamine in said reaction product.

9. A size produced by the process of claim 8.

10. Paper composed of cellulosic fibers sized by a uniformly distributed content of from about 1% to 5%,

based on the dry weight of the fibers, of the cationic rosin size formed by reacting an ester gum at about 175- 250 C. with a water-soluble polyalkylenepolyamine containing at least three nitrogen atoms, the ratio of the rosin solids in said ester gum to the nitrogen atoms of UNITED :STATES PATENTS 2,304,369 Morgan te a1. Dec. 8, 1942 

10. PAPER COMPOSED OF CELLULOSIC FIBERS SIZED BY A UNIFORMLY DISTRIBUTED CONTENT OF FROM ABOUT 1% TO 5%, BASED ON THE DRY WEIGHT OF THE FIBERS, OF THE CATIONIC ROSIN SIZE FORMED BY REACTING AN ESTER GUM AT ABOUT 175*250* C. WITH A WATER-SOLUBLE POLYALKYLENEPOLYAMINE CONTAINING AT LEAST THREE NITROGEN ATOMS, THE RATIO OF THE ROSIN SOLIDS IN SAID ESTER GUM TO THE NITROGEN ATOMS OF SAID POLYALKYLENEPOLYAMINE BEING BETWEEN ABOUT 3:7 AND 2:3, AT LEAST UNTIL THE REACTION PRODUCT AS ITS ACETATE SALT FORMS A COLLOIDAL DISPERSION WHEN AGITATED WITH WATER. 